Telephone trunking and supervisory system.



w; L. CAMPBELL. TELEPHONE TRUNKING AND SUPERVISORY SYSTEM.

APPLICATION FILED FEB. 26, 11907- Iatented July 18, 1916.

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W. L. CAMPBELL. TELEPHONE TRUNKING ANDSUPERVISORY SYSTEM.

y W Wm 7 WWW m 5 W m 1 a UNITED STATES PATENT OFFICE.

WILSON L. SAMPBELL, OF CHICAGO, ILLINOIS. ASSlifi-NOR. BY MESNEASSEGNMENTS, T9 FIRST TRUST AND SAVINGS BANK.

TRUSTEE. OF CHICAGO, ILLINGIS.

TELEPHQNE TRUNKING AND SUPERVKSQBY SYSTEM.

Specification of Letters Patent.

Ilatcntcd July 1916.

Application filed February 26, 19071 Serial Ho. 359,406.

To 0/5 hom it may concern Beitflmown that l. Wimox L. Cameraman oi thellnited States of America. and re. lent of Chicago. (look county.Illinois. have invented a certain new and 11S?- ful luiprm'enicnt in'llelephone Trunking and Supervisory Systems. of which the following. a:qiecitmation. I My invention relates to telephone systems. and moreespecially to systems in which means are provided for enabling a callingsubscriber to establish connection with the desired line, without theaid ot' operators.

Objects of my invention are to provide means for enabling any subscriberto establish connection with a special service line. such. for example.as a line leading to one or more operators positions. whereby the saidcalling subscriber may report trouble or receive information or obtainsuch other service as may be desired; to provide a special service linehaving provisions for en abling the first o 'ierator thereon to transferall incoming calls to the next operator. and for enabling the secondoperator to transfer the calls to' the third operator-{and so onthroughmit the series of operators. according to requirements: toprovide an arrangement by which a calling subscriber may extendconnection from his line over one. or more trunk lines to a connector,and may then cause the said onnector to establish connection with aspecial service line leading to one or more operators the said connector being prefe ably what is commonly known as a rotary connectorthatis to say. a connector which will automatically rotate like a trunkselector until it finds an idle line; to provide lamp signals forattracting the attention of the operators on the special service lines.which lamp. signals can be brought into operation by the callingsubscriber when he presses his ringing key said lamps being controlledby relays which are responsive to the ringing-current; to provide pilotlamps tor the different operators positions. one pilot lamp being commontoall the operat .1; who occupy first position on the group of specialservice lines. another pilot lamp being common to all operators hooccupysecond position on the group of special service lines. and so onthroughout the series of positions on the said special service lines;and to provide certain details and features of improvement generaleilici n and ci'nnbii'ations lending to increase the 7 c y andserviceability of a system of this particular character.

To the foregoing and other useful ends, my inven irm ms s in matters heein disclosed and min i.

In the account. ring drawings. Figure 1 is a 'liz-i' rain sh ing asubstation A (:onneeted with a central otlicc comprising a centralbattery li li;l\ lug. preferably. its positive terminal grounded at t.and automatic swit hes t. l and ll. in conncctioi'i with which I hareelected to explain my invention. The switch (7 is commonly known as afilstsr-lectoi; the switch D as a second selector. and the switch E as aconnector. At F is represented. a lmsy-signaling machine. and at ll isshown a ringer generator.

in :1. which is a, diagram. are shown several manual circuits comprisedin my invention and located at the central ollice, at which place i. Jand K represent, respecti ely. a fir t. second and a last operatorsposition. Obviously. however, other such operat rs" positions may beinserted. as. for example. between the positions J and K, substantial yas position J is placed between l and K. In connection with these m nualcircuits there shown a night alarm rangement L. The keys (1. Z) and c,whereby the incoming trunk line may be extended from one operator'sposition to another. are shown in normal position. The arrangement ofthe system is such that the attendant at position I may. by operatingthe springs at the left of key a. extend the trunk line (shown leadingfrom Fig. 1 to Fig. 2. and which. while key a. normal, terminates atposition I) to the operator at .l where the signal will be receivedwithout signaling position I. Similarly the .optrator at J may operatethe springs on the left of key 7; and in turn transfer the incomingtrunk line to the next position.

Figs. l and 2 taken together show means whereby or automatic subscribermay establish conn ction with a trouble-recording or other oyu-ratorsboard The substation A may be of any suitable type. and comprises, forexample, a receiver 2. switrlrhook 3. inductionoil 4 (which coilconsists of the primary winding 5 and secondary winding (3). transmitter7, local battery 9 and the ringer 9. In addition to the above-mentionedparts an impulse Wheel .at once be recognized.

10 is provided which has the usual vertical impulse teeth 11 that areadapted to operate the vertical impulse spring 12. The impulse wheelcarries the rotary impulse tooth 13 which operates the rotary impulsespring H. The switch-hook has radiating from its body a number ofcam-arms 15, 16 and 17, and is pivotally secured to the keyboard (notshown) at the point 18 about which it operates when the receiver isremoved. The operation is produced by a spring (not shown) for thepurpose of changing certain circuit connections to be disclosed. Thecam-arnr15 controls the so-called locking arm 19. After the dial isrotated the lock ing arm 19 occupies the position shown at substation A,the mechanical operations of which are well known; and at the same timethe coiiperating ground springs 20 and 21 engage, thus placing theground post 22 in contact with the substation ground G, whereby, whenthe subscriber releases the dial after rotating it as described, thevertical impulse teeth 11 will then cause the vertical impulse spring 12to come into contact with the ground post 22; and immediately after, therotary impulse tooth 13 causes the rotary impulse spring 14 to come intocontact with the same ground post 22. 'hen the switch-hook is down thecam-arm 17 maintains a contact with the spring 23, thereby bridging theringer 9 across the line. The springs 21 and 25, and 26 and 27 are thendisengaged, and the primary circuit including the winding 5 in serieswith the transmitter 7 and local battery 8 is interrupted by theseparation of the springs 26 and 27. The disengagement of the springs 24and 25 removes the secondary winding 6 in series with the receiver 2from across the line. The signaling device where by a subscriber maysignal another after a connection has been established comprises apush-button 28 and a spring '29, which latter normally engages thecontact point 30; but, when the push-button 28 is pressed the spring 29leaves the contact point 30 and engages the contact point 31 which isconnected with Means whereby the subscriber may'release the centralstation apparatus brought into service comprises three springs 32, 33and 31, known as the release springs and so controlled by the cam-arln16 that when the switch-hook descends the three release springs arebrought into contact, thereby grounding both of the subscrlbefs lineconductors simultaneously.

The first-selector C is of the well-known type disclosed in UnitedStates Patent No. 815,321, granted March 13, 1906, to Keith, Erickson &Erickson, and upon referring to Fig. 1 its various relays and magnetswill As illustrated, 61 and 62 indicate the vertical and rotary line thesubstation ground G,

relays by means of which the switch is operated; 61 indicates thebridge-cut-off relay for controlling the connection between said linerelays and the battery; 37 indicates the vertical magnet for raising theshaft vertically; 38 indicates the rotary magnet for rotating the shaftand shaft wipers; 3 9 indicates the private magnet by means of which theside switch is controlled; 41" indicates the release magnet forrestoring the switch after operation; and 40 indicates the Mick-releaserelay by means of which the selector is released after the side switchpasses to third position.

The second-selector D is quite similar to the first-selector C andcomprises vertical and rotary line relays 35 and 36, respectively.vertical and rotary magnets 37 and 38, private magnet 39, release relay40 and a release n'iagnet 41. Furthermore, it will be noticed that thebridge-cut-oil' relay of the second-selecti'ir does not appear, the linerelays 35 and 36 being connected directly to the battery lead; also,that the line relays 35 and 36 are provided with the trunk-releasesprings 42 and 43 which are similar to the release spring of theconnector disclosed in United States Patent, No. 815,176, granted March13, 1906, to Keith, Erickson & Erickson.

The connector switch E, commonly known as a rotary connector, is amodification of the connector disclosed in the said connector patent.The vertical and rotary line relays H and 45, respectively, are providedwith the usual connector springs. The vertical and rotary magnets 16 and17 are'under the control of the vertical line relay 44.

.Inaddition, the rotary magnet 17 is provided with the interrupterspring 18 by means of which the said connector may be automaticallyrotated (like the first-selector) when the private Wiper engagesgrounded contact points. Hence, with this provision, whereby theconnector may be auton'iatically rotated in addition to being rotated inthe usual manner, the rotary element combines the rotary characteristicsof the first-selector and the connector disclosed in both of saidpatents. A new feature of this connector is the private relay 19 whichis controlled by the rotary line relay 45. The former in turn controlsthe private magnet 50 under certain conditions, as will be more fullyexplained hereinafter. The function and operation of the back-bridgerelays 51 and 52 are well-known; also, the ringer relay 53 and therelease magnet 54 are controlled and operated as explained in the saidconnector patent.

Atthe signal-receiving board the operaators set (Fig. 2) comprises a keya which is adapted to operate the group springs, as shown. The relay 55is provided for closing a circuit through the signal lamp 56 ofoperators.

which indicates to the attendant that a subscribe! has seized theallotted line. The pilot relay 5? is common to a group of trunk linesignal lamps, of which group lamp 556 isa member. The said relay, whenenergized, operates to close a circuit-through the pilot lamp 58. At (1is shown an operator's telephone set.- At the second operators positionJ is shown a duplicate of the apparatus and circuits of the position I.The only difference in the last position; K is found in the key 0; forthere the left-hand group of springs, whereby the trunluline is extendedto the next succeeding position, is omitted.

Assuming that the automatic "subscriber A Wishes to communicate withthec'entral oflice, he may do so by calling a number that will placehimin connection. with theirotary connector E, which connector he thenoperates in order to establish connection with a trunk line leading tosome operator or sets His ohjqect in doing so may be to report trouble,obtain intorin'ation, call for toll connection, or any other similar ob:ject. To start with, it will be assumed that the number of the line thatto the operators sets, shown in Fig. 2, is 8111. The number 8111,however, may be given to a set of lines, each line terminating in adifferent manual set, such as the one shown in Fig.

2. Theobj'ect of such an arrangement is that if the firstdine ofgroupSilt is busy the rotary connector E will automatically otate until itfinds the first idle line, in the same manner that the selector switchesoperate when they are selecting trunks. Obviously, such an arrangementis necessary in an exchange where a number of subscribers are liable tocall very close together.

It will be obvious, furthermore, that the connector E may be providedwith a number of such groups, each of which may be given a separate anddistinct number, such as 8115,

8121, or any other number which is applica are to such a connector, eachof: which groups may be used for an absolutely diii erent and distinctpurpose. V-Zith' the arrangement shown in Fig. l the last, contact ofthe group to which the line leadirg. to Fig. 2 belongs is connected withthe busy machine F, so that if all the lines of that. particular groupare busy the caliing subscriber may, when the corniector passes onto thelast set of con-- tacts, receive the busy signal.

When the subscriber at substation it starts to call the group 8111, heoperates the dial for the first digit 5*, as a result grounding thevertical and rotary line conductors 59 and 60, whereby the vertical androtary line relays 61 and 62 become energized and operate in thewellknown manner, with the result that the firstselector side switchpasses to third position, and that the selector switch-shaft Wipers 63,4 and are placed in contact with the c0nafter the relay 49 deenergiirgitact point 72, side switchwipe lays 3-5 and 36, respectively, thesecondselector D alternately energizeand' operate to extend thesubscribefis linc' conductorsffiil and GO to the connector TL- b y wayof the shaft wipers 66 and 67, substantially as'lthe first-selector Coperated 'eiftentli tlieflirie conductors59 and (30 todth 's e j Theground impulses given; to" the line conductors 59 and 60,respectivelyffor th'ef last two digits 1 and 1 aree'fi'ectivejin puating the connector E. When the conductor 59 is grounded for the thirddigitl the vertical line relay 44 becomes energi /Jed and operates toplace the springs 63 and 69 in contact, whereby an energizing circuit iscompleted in the well' knoav'n manner through the vertical magnet 46,with the result-that the shaft wipers'70, 71fand 72 are raised one step.When the rotary line relay 45 energizes as a result of the groundimpulse to the rotary line conductor 60, the springs 73 and 69 engageand'c-lose acircuit through the private rel ay 49 extending from groundG through the springs 6 andi73, through the private relay 49 to thebattery, lead 74, thence through battery 13 to ground G. The privaterelay, upon energizing, operates in turn ,'to disengagerthe springs 7 5and 7 6, and tothereby' place the springs 7 7 and 78 in contact. Theengage ment ofthe springs 77 and 78 ,closes an'eners gizing circuitthrough the;privater magnet" 50 extending from'ground G lthrough thesprings 77 and 7 8, through the private rnage net 50 to the battery lead74, thence through battery B and to ground Gr, QiThe private magnetoperates to permit [theside switch wipers 79, 80, 8I'an'd 82to'pas'sfrom to second position, whereby the. rotary'm'ag.

net 47 comes under the control of the ve ti-' cal relay 4%. The lastdig'it beiui", vertical line relay 44, upon energizii I an energizingcircuit through the rotary magnet 47 which operatesto'itotate thcsha'ftwipers 70, 71*and 72 onto the first c'onta of the first level. Now whenthela rt-daily impulse operates the rotary linc one of two resultsoccurs, nairfely their case-of the side switch from. second to t tion,at once, or the connectorsha. matically rotated until anidle liisjils ifthe private wiper 72, busy. This is bmught When the private relay49,,ai1d 1 I urn the private magnet 50. energize and o pelifataaspreviously explained, the en gluing circuit through the Private magnetmaintained *iid circuit extending from the grounded 4 Pr vateer-m -vfound, in first line, fa lew point 83, private magnet 'spriiigf '85,through the Winding tin pri at magnet 50 to the battery lead 74, thencethrough battery B and to ground G. The private magnet thus remainsenergized and retains the side switch in second position as long as thewiper 72 engages a busy or grounded contact. Furthermore, when theprivate magnet thus energizes, the spring 86 is shifted out ofengagement with the spring 87 and into engagement with the spring 88,whereby a new energizing circuit is completed through the rotary magnetvate magnet is broken, whereby the said' magnet deenergizes, breaks thecircuit through the rotary magnet 47 and perm-its the side switch topass to third position, extending the line conductors 59 and to thetrunk conductors 90 and 91, respectively, which latter-lead to thetoll-board or desk equipped with my signal-receiving apparatus, as shownin Fig. 2.

\Vhen the subscriber at substation A presses the signaling button 28 theringer relay 53 becomes energized in the wellknown manner, and operatesto bridge the ringer generator H across the trunk conductors 90 and 91,whereby a signaling current is transmitted from the springs 92 and 93 tothe side switch wiper 79, contact point 94, shaft wiper 70, verticalconductor 90, through the springs 95 and 96, springs 97 and 98, winding99 of the lamp relay 55,

through the springs 100 and 101, 103 and 102 to the rotarytrunkfconductor 91, shaft wiper 71, contact point 104, side switch wiper80, ringer relay springs 105 and 106,

thence to the generator H. The signaling current in passing through thewinding 99 energizes the relay 55, which operates to close the springs107 and 108 in contact. The engagement of the springs 107 and 108completes an energizing circuit through the locking winding 111 of therelay 55 and also through the signal lamp 56 in series with. the pilotrelay 57. The circuit through the locking winding 111 extends fromground Gr to the springs 109 and.110, springs 107 and 108. through thewinding 111, conductor 112 to the night alarm switch 113, to the batterylead 74, thence through battery B and to ground G. The operator inresponse to the signal operates the key a in such a manner that thesprings 97 and 98, 100 and 101, and 1.09 and 110.,disengage, and thesprings 97 and 116, and 101 and 117 engage. The disengagement of thesprings 109 and 110 breaks the energizing circuit through the lamp 56and the locking winding 111. The engagement of the springs 97 and 116,and 101 and 117 bridges the operators telephone set d across the trunkconductors 90 and 91, thus connecting with the calling subscriber atsubstation A. The subscriber at substation A and the operator at I maythen communicate over a circuit shown by the heavy lines. If for anyreason it is desired that operator J shall take charge of all callscoming in on the trunk conductors 90 and 91, the operator at position Ioperates the key a, so that the springs 96 and 102 disengage the springs95 and 103 and engage the springs 118 and 119, respectively, therebydisconnecting'the line from position -I and extending the conductors 90and 91 to the second position J. Now when the line is seized the signalwill be received atIposition J and the signal lamp 120, relay 121, pilotrelay 122and pilot lamp 123 will operate, as explained in connectionwith position I. Fu 'thermore, the line may in turn be extende toposition K by the operation of the key b,,"so that the springs 124 and125 disengage from the springs 126 and 127 and engage the springs 128and 129, respectively, whereby the line is disconnected from theposition. J and again extended to the position K. .The signaling currentnow passes from the conductor 90 through the springs 96 and 118 of keya, springs 124 and 128 of key I), springs 130 and 131 of key 0, winding132 of relay 133, springs 134 and 135, springs 129 and 125} of key 6,springs 119 and 102 of key a to the conductor 91. The relay 133, uponenergizing, closes a circuit through the locking winding 136 of therelay 133, and a circuit through the pilot relay 137 in series with thesignal lamp 138. The locking circuit through the winding 136 extendsfrom ground Gr through the springs 139 and 140, springs 141 and 142,winding 136 of the relay 133, conductor 112 (assuming that the nightalarm switch 113 occupies the position shown byf'dotted lines) throughthe night alarm relay 143 to the battery lead 74, thence through batteryB and to ground G. The circuit through the lamp 138 extends from groundGr through the springs 139 and 140, and 141 and 142, lamp 138, pilotrelay 137, conductor 112, thence to the battery B through the nightalarm relay, as previously traced. The pilot relay 137 operates to closethe springs 144 and 145 in contact, whereby acircuit through the pilotlamp 146 is closed. The night alarm relay 143, upon energizing, closesthe springs 147 and 148 into contact, and a circuit is thereby closedthrough the night signal bell 149.

When the key a is operated the springs 130 and 135 disengage fromthesprings .131

and 134 and engage the springs 150 and 151, respectively, whereby thelamp relay 133 is removed from across the extended line and theoperators set 6' is bridged instead. Furthermore, the springs 140 and139 disengage, and the circuit through the signal lamp 138 and lockingwinding 136 is broken, thus permitting the lamp relay 133,'the pilotlamp relay 137 and the night alarm relay 143 to return to normalposition. It will be understood, of course, that the night alarm relay143 (which may be cut in and out of the circuit by the switch 113) mayor may not be used, as desired, the object of such tors 90and 91, and ifeach trunk is provided with an equipment similar to the one shown inFig. 2, then the pilot lamp 58 may be operated whenever a call comes into any one-ofthe :operators I of the various boards. If any of the trunklines are extended to the operator'J, the pilot lamp 1'23 may beoperated when-a call comes in to any operator J ;'and if any of thelines are extended to the operator K, the pilot lamp 146 may be operatedwhenever a call comes in to any one of the operators of the lastposition.

The relays may be of any suitable resistance, butgood results have beenobtained when the lamp relays55, 121 and 133 are wound to a resistanceof five hundred ohms in each winding,andthe pilot lamp relays '57, 122and 137 and the night alarm relay 143 to a resistance of'one andeight-tenths ohms each. j

From the foregoing it. will be seen that a calling. subscriber extendsconnection from 'his line over one or more trunk lines -to a connectorwhich is capable'of picking out an idle special service line. On thisspecial service line are one ormore operators positions, and eachoperator, except the last of course, can transfer all incoming calls tothe next opera-tor, according to requirements.

' It will be understood, of course, that the said connectors can beemployed on a percentage basis.that isto say, it will be understood thatthe connectors can be less in number 'thanthe total number ofsubscribers. It will also be understood that with suchan ar-' rangementthe second-selectors; will in number-than the total number ofsubscribers, while the total number of firstselectors will be the sameas the total number of subscribers, inasmuch as first-selectors areemployed .as individual switches for the different subscribers. tor, asexplained, is adapted to rotate like a trunk selector until it finds anidle special service line.

What I claim as my invention is 1- 1. A telephone system comprising aspecial service line, a plurality of operators" positions on said line,automatic means by Each connecwhich a calling subscriber extendsconnection to said .line, and a switch at one position for tran ferringincoming calls to another position: v

2. A telephone system comprising a special service line, automatic meansby which a calling subscriber extends connection to said line, aplurality of operators positions on said line, and oneor more switchingdevices by which each operator, except the last, may transfer incomingcalls to the next operator 3. A telephone'system comprising a spe-- cialservice line, a connector adapted to make connection with said line,automatic means" for trunking a calling subscriber into connection withsaid connector, means by which the subscriber controls the connector toestablish connection withthe special service line, a plurality ofoperators positions on said line, and means for transferring incomingcalls from one position to another.

4. In a telephone system, the combina-' tion of a special serviceline, aplurality of operators positions on said line, means by whicheach'operator, except the last,"may direct the incoming calls to thenext operator, an automatic connector adapted -to connect with saidline, automatic means for trunking a calling subscriber into 00111160tion with said connector, and means by which the subscriber controls theconnector to complete connection with the said line.

' 5.'A telephone system comprisinga spe cial service line, a relayhaving two -W1Ii(1 1 ings one of which is normally bridged aci 05s thesaid, line a battery, a local circuit-ineluding said battery and-the,other windmg of the relay, said relay controlling said local circuit,circuit controlling .means by which the calling subscriber projects current onto the line to initially energize said relay, and automaticrogressively -m0vable switching apparatus by which the callingsubscriber extends connection to said line prior to the energizing ofthe relay.

6. A telephone system comprising a special service line, a lurality ofoperators telephones 'on' said ine, normally. disconnected therefrom, alamp signal for each telephone, means by which each operaticautomatically retires her allotted signal when she connects hertelephone with the line, automatic means by which a calling subscriberextends connection to said line, and means by which one operator maydirect the incoming calls to the next operator.

7. In a telephone system, the combination of agroup of special servicelines, a plurality of operators positions on each line, automatic meansfor trunking a calling subscriber into connection with one of saidlines,- individual signals for the operators, :1 pilot lamp common toall operators occupying first positions on said lines and a pilot lampfor each additional group of operators occupying like positions on saidlines.

8. In a telephone exchange system, the combination of a line, aplurality of operators or attendants telephones on said line, a visualsignal for eaclrtelephone, a calling subscribers line, automatic meansfor connecting the calling line with the other said line, parallelcircuits for said visual signals,.relay means controlling said circuits,and means by which one operator or attendant may direct the incomingcalls to the visual signal of the'next operator.

9. Ina telephone exchange system, the combination of a line, a pluralityof operators or attendants telephones on said line, a call-receivingdevice for each telephone, a calling subscribers line, automatic meansfor connecting the calling line with the said other line, and means bywhich one operator may disconnect from the line and direct all incomingcalls to the next operator.

10. In a telephone exchange system, the combination of a line, a callingsubscribers line, automatic means by which the calling subscriberconnects his line with the said first-mentioned line, a plurality ofoperators telephones on said first-mentioned line, acall-signal,,associated with each telephone, and means by which oneoperator may direct the incoming automatic calls to the next operator.

11. In a telephone system, a line with a plurality of operators orattendants positions -thereon, means to automatically extendconnection'to said positions, the line being normally open at eachposition, and means for closing the line at each position and thussuccessively transferring calls from one operator to the next.

12. In a telephone system, a line, a plurality of call-receivingpositions on saidv line, means to automatically extend connection tosaid positions, the line belng normally open at each position, means foreX- tending the line from one position to an other to transfer incomingcalls.

13. In a telephone system, a plurality of trunk lines, a relay bridgedacross each trunk and individual thereto, a signal controlled by eachrelay, a relay common to a plurality of trunks and controlled by all ofsaid inst-mentioned relays, a supervisory signal controlled by saidlast-mentioned relay, a

source of current for operating said individual relays, and aprogressively movable switching device for controlling connection fromsaid source of current for operating said relays.

14. In a telephone system, a plurality of trunk lines, a plurality ofoperators sets associated. with each trunk'line, a relay bridged acrosseach trunk and individual thereto, a supervisory signal controlled bysaid relay, a second relay controlled by a plurality of saidfirst-mentioned relays, a second supervisory signal controlled by saidlast-mentioned relay, a source 01 current for operating said bridgedrelays, and progressively movable automatic switching apparatus forcontrolling connection from said source of current for operating saidrelays.

15. A telephone system comprising a special service line, a connectoradapted to make connection with said line, automatic means for trunkinga calling subscriber into connection with said connector, circuit meansby which the subscriber controls the connector to establish connectionwith the special service line, a lurality of operators positions on saidinc, and circuit means for transferring incoming calls from one positionto another.

16. Ina telephone system, the combination of a special service line, aplurality of operators positions-on said line, circuit means by whicheach operator, except the last, may direct the incoming calls to thenext operator, an automatic connector adapted to connect with said line,automatic means for trunking a calling subscriber into connection withsaid connector, and circuit means by which the subscriber controls theconnector to complete connection with the said line.-

17. A telephone system comprising a special service line, a plurality ofoperators telephones on said line, normally disconnected therefrom, alamp signal for each telephone, circuit means by which each operatorautomatically retires her allotted signal when she' connects hertelephone with the line, automatic means by which a calling subscriberextends connection to said line, and circuit means by which one operatormay direct the incoming calls to the next operator.

18. In a telephone exchange system, the combination of a line, aplurality of operators or attendants telephones on said line, a visualsignal for each telephone, a calling subscribers line, automatic meansfor connecting the calling line with the other said line, parallelcircuits for said visual signals, relay means controlling said circuits,and

circuit means by which one operator or attendant may direct the incomingcalls to the visual signal of the next operator. I 19. In a telephoneexchange system, the combination of a line, a plurality of operators orattendants telephones on-said line, a call-receiving device for eachtelephone, a calling subscribers line, automatic means for connectingthe calling line with the said other line, and circuit means by whichone operator may disconnect from the line and direct all incoming callsto the next operator.

20. In a telephone exchange system, the combination of a line, a callingsubscribers line, automatic means by which the calling subscriberconnects his line with the said first-mentioned line, a plurality ofoperators telephones on said first-mentioned line, a call-signalassociated with each telephone, and circuit means by which one operatormay direct the incoming automatic calls to the next operator.

21. In a telephone exchange system, the combination of a line, aplurality of operators orattendants telephones on said line,

a visual signal for each telephone, a calling subscribers line,automatic means for connecting the calling line with the other saidline, parallel circuits for said visual signals,

relay means controlling said circuits, and means by which one operatoror attendant may direct the incoming calls to the visual signal of thenext operator.

,maydisconnect from the line and direct all incoming calls to the nextoperator.

23. In a telephone exchange system, the combination of a line, a callingsubscribers line, automatic means by which the calling subscriberconnects his line with the said first mentioned line, a plurality ofoperators telephones on said first mentioned line, a call signalassociated with each telephone, and means by which one operator maydirect the incoming automatic calls to the'next operator. 1

Signed by me at Chicago, Cook county, Illinois, this 20th day ofFebruary, 1907.

' WILSON L. CAMPBELL.

.Witnesses:

J. NORBY,

